Aphids what to do with them?

Some plants in our system are having a lot of aphids others don't attract them at all.

Now what should I do?
Murray Hallam suggests to use molasses with a drop of detergent for an even spread.
Other voices say its best to use nettle manure.
A visiting journalist proposed alcohol (spirit) but for aquaponics? Maybe if you make sure it does not mix with the water. In theory it should vapour rapidly, right...

What are your ideas on getting rid of those small juice drinking creatures?